1. 2.9 Photosynthesis Applications:
Understanding:
Photosynthesis is the production of carbon compounds in cells using light energy
Visible light has a range of wavelengths with violet the shortest wavelength and red the longest
Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours
Oxygen is produced in photosynthesis from photolysis of water
Energy is needed to produce carbohydrates and other carbon compounds
Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis
Applications:
Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis
Skills:
Design of experiments to investigate limiting factors on photosynthesis
Separation of photosynthetic pigments by chromatography
Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis
Nature of science:
Experimental design: controlling relevant variables in photosynthesis experiments is essential

2. Sunlight
Glucose
Water
Oxygen
Carbon dioxide

3. Photosynthesis

4. Photosynthesis
Plants are able to make their own energy using sunlight and simple compounds.
Carbon dioxide + water  glucose + oxygen
Produces carbon compounds
Understanding:
Photosynthesis is the production of carbon compounds in cells using light energy

5. Photosynthesis
Light energy converted to chemical energy for photosynthesis Endothermic (energy goes in)
Understanding:
Oxygen is produced in photosynthesis from photolysis of water
Energy is needed to produce carbohydrates and other carbon compounds

6. Photosynthesis
Photolysis splits water to release electrons needed in other stages of photosynthesis Only happens when light present (photo)
Understanding:
Oxygen is produced in photosynthesis from photolysis of water
Energy is needed to produce carbohydrates and other carbon compounds

7. Effects of Photosynthesis
Prokaryotes completed photosynthesis initially 3,500 million years ago Followed by algae and plants Caused an increased oxygen concentration in the atmosphere
Applications:
Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis

8. Caused by reduction in greenhouse gases
Glaciation
Caused by reduction in greenhouse gases
Applications:
Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis

9. Oxidation
Dissolved iron in water oxidized causing it to precipitate on the sea bed Caused a distinctive rock formation of iron oxide Banded iron formation
Applications:
Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis

10. Oxidation Applications:
Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis

11. Wavelengths
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Light is made up of many wavelengths Some wavelengths are invisible to us
Understanding:
Visible light has a range of wavelengths with violet the shortest wavelength and red the longest

12. Wavelengths
Too short to see: X-rays, UV rays Too long to see: Infrared Visible light range from 400 to 700 nanometres
Understanding:
Visible light has a range of wavelengths with violet the shortest wavelength and red the longest

13. Wavelengths
Wavelengths of light detected by human eye also used in photosynthesis They are the most abundant wavelengths on earth so plants have adapted to use these
Understanding:
Visible light has a range of wavelengths with violet the shortest wavelength and red the longest

14. Pigments
Pigments are substances that absorb light – they appear colored to us If a pigment absorbs all colours, it appears black as it emits no light If it looks white – the object reflects all colours Some pigments only absorb certain wavelengths of light
Understanding:
Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours

15. Pigments
Gentian flower absorbs all colour except blue So it appears blue The blue wavelength from sunlight is reflected and can pass into our eye.
Understanding:
Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours

16. Chlorophyll
There are various forms of chlorophyll but they all appear green to us They absorb red and blue light easily Green light is absorbed less effectively so is reflected This is why plants look green!
Understanding:
Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours

17. Spectra
Action Shows rate of photosynthesis at each wavelength of light Absorption Percentage of light absorbed at each wavelength for each pigment
Skills:
Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis

18. Rules for drawing spectra
Action
Absorption
Both
Y-axis should be used for rate of photosynthesis – often given as a percentage of the maximum rate (0-100%)
Y-axis should be labelled % absorption (0-100%)
X axis should have label: wavelength (nm)
Scale from nm for wavelength
Skills:
Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis

20. Chromatography
Chloroplasts have many types of chlorophyll and other pigments Because they absorb different wavelengths of light they look different colours to us We can separate these pigments by chromatography
Skills:
Separation of photosynthetic pigments by chromatography

22. Limiting Factors What can affect the rate of photosynthesis?
Too cold/too hot
= slower photosynthesis
Even if other variables are there
Optimum temperature = faster photosynthesis
Less light = plant photosynthesises slowly
Even if there is a lot of water and carbon dioxide
More light = faster photosynthesis
Less carbon dioxide = slower photosynthesis
Even if there is a high light intensity
More carbon dioxide
= faster photosynthesis
Understanding:
Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis

23. What can slow the rate of photosynthesis?
Limiting Factors
What can slow the rate of photosynthesis?
Light Intensity
Graph:
Description:
Carbon dioxide
Graph:
Description:
Temperature
Graph:
Description:

24. Planning an investigation
How ONE factor can affect the rate of photosynthesis. You can choose which one. Hypothesis Variables Equipment Method Risk Assessment What are the different ways you can measure the rate of photosynthesis?
Skills:
Design of experiments to investigate limiting factors on photosynthesis
Nature of science:
Experimental design: controlling relevant variables in photosynthesis experiments is essential

25. Planning an investigation
Direct and most accurate Measure uptake of carbon dioxide (carbon dioxide monitor) Measure production of oxygen (volume of bubbles produced in measuring cylinder) Indirect and least accurate Measure production of carbohydrates (measure sections of leaf) Measure the increase in overall mass of plant over time
Skills:
Design of experiments to investigate limiting factors on photosynthesis
Nature of science:
Experimental design: controlling relevant variables in photosynthesis experiments is essential